Conventional heating and air conditioning ventilation systems employ primary particle filters to prevent airborne debris from entering the system. Large particles such as leaves, dirt, hair, and rug lint, are ideally stopped by the filter to prevent interfering with the operation of the system. Excessive debris creates a fire hazard, for a heater operates at a temperature sufficient to start combustion.
The aforementioned filters are designed only to prevent large debris from entering the heater system. Particles as large as dust are not inhibited from a conventional filter. This phenomenon is evident when a heater is used infrequently. When the heater is started after a period of non-use, the heater burns the dust leaving a pungent smell capable of setting off smoke detectors.
While particles may be an annoyance in a ventilation system, the distribution of particles is dangerous for a person having health related problems. For instance, airborne particles may cause an asthma attack; bacteria spores may cause an allergic reaction; or chemical vapors may result in a rash. While many vapors cannot be detected by human senses or even sensitive equipment, many such vapors can accumulate in a person. For example, carpeting may propagate formaldehyde, a known carcinogen that may not have a detectable accumulation effect for years.
While conventional ventilation systems of the prior art have used a filter in order to protect the actual heating and ventilation components, only recently has the art progressed to the point of filtering the air for the purpose of protecting the recipients of the ventilation.
One known filter used in ventilation systems is the HEPA or high efficiency particle arresting filters which are approximately 73% efficient at trapping particles larger than 0.3 micron particles and 95% efficient at trapping particles larger than one micron. The problem occurs in that a majority of bacteria range in the size from 0.4 to 5 microns and can be easily trapped by a filter wherein the filter operates as a breeding ground for additional bacteria which can be sloughed off into the ventilation system. Viruses are much smaller, ranging in size from approximately 0.003 to 0.06 microns and are easily passed through a conventional filter for distribution throughout the ventilation system. While a HEPA filter has certain advantages, it does not treat bacteria or vapors and is cost prohibitive for the average residential or commercial property. It is not practical to trap all particles wherein variations and substitutions for particle trapping form the prior art in an effort to lessen the bacteria growth and particle distribution throughout a system.
In many situations a conventional filter, even a HEPA filter, is an organism amplifier. It is not uncommon to find a filter that is wet when no other water is apparent, the moisture content being the advent of a bacterial slime. In many instances, even if filters are changed regularly it is not uncommon to find filters filled with penicillium spores. When the filter is changed, it is not uncommon for the spores to be released into the ventilation system. Despite the frequency of filter exchanges, many closed ventilation systems have led to what has been called a "sick building". These buildings are designed to prevent energy loss by restricting air leakage. This air restriction further traps moisture in such buildings including chemical vapors from various consumer products such as formaldehyde, carbon monoxide, tobacco smoke, ammonia and so forth. Bacteria accumulation produced by wet cooling coils aggravates the condition by providing a breeding ground for bacteria wherein the ventilation system recirculates the bacteria throughout the building. Sick buildings, whether they be residential or office buildings have symptomatic complaints from the occupants for a variety of symptoms including headaches, fatigue, infections, neurological and psychological disorders, irritability, forgetfulness, burning of the eyes and throat, and so forth, which do not fit the pattern of any particular illness and are difficult to trace to any specific source.
In an effort to address these problems, various patents address items for use with ventilation systems. U.S. Pat. No. 4,990,313 discloses an ultraviolet light placed in-line in an air return system mounted downstream of a cooling coil. The light is disclosed for destroying of bacteria accumulations yet does not address proper pre-filtration of bacteria laden air bypassing the effectiveness of the light. Further, the disclosure does not provide for control of vapors or removal of dead spores which creates additional harmful particles in and of themselves.
U.S. Pat. No. 5,225,167 discloses a room air sterilizer utilizing an ultraviolet light having a pre-filter mounted before the light followed by a HEPA filter. While the patent discloses the advantages of a pre-filter and post filter, the device fails to teach filtration that is efficient or affordable. Further, the system does not address the control of chemical vapors or the possibility of ozone production from the ultraviolet light.
U.S. Pat. No. 5,015,442 discloses a filter system with an ozone producing ultraviolet light followed by an ozone decomposing catalyzer to destroy excess ozone. The intentional generation of ozone gas in a confined area is not acceptable for residential or point of use.
U.S. Pat. No. 5,186,903 discloses an apparatus for treating indoor air. This invention is directed to air contamination found in commercial, industrial and residential structures. Used in conjunction with a HVAC System, the device purifies air as well as removes trace substances of chemicals used in the cleaning and maintenance of a building as well as other substances found in air tight buildings. This invention does not disclose the use of an ultraviolet light and relies upon a molecular catalytic cracking of heavy hydrocarbons by use of an electrified catalyst, such as ozone, for destruction of constituents before removal through a filter system.
U.S. Pat. No. 5,298,043 discloses a complicated filter system for smoke and polluted air relying upon a set of sprayers that wash and moisturize the air before reuse.
U.S. Pat. No. 4,604,110 discloses still another air filter element for use in removing odors from indoor air systems based upon a mixture of silica gel, activated carbon and a fungicide/biocide to prevent micro-organisms from growing on the bed of the activated carbon.
U.S. Pat. No. 4,682,992 discloses a substance used for coating of air filters in order to prevent or inhibit micro-organisms from growing. This is not a filtration system but discloses a coating mechanism that would be used with air filter systems.
Thus, what is lacking in the art is an affordable filtration system for use within a conventional ventilation system capable of reducing or eliminating airborne particles, bacteria, and chemical vapors with a means for reducing the moisture content of the filters and made of materials to prohibit bacterial growth.